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https://issues.apache.org/jira/browse/HBASE-5494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13220680#comment-13220680
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stack commented on HBASE-5494:
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I think maybe region locks is for later. Meantime, getting a read lock on the
table when doing a split or merge might carry us a long way.....before we need
region specific locks.
@Mubarak Todd has a good point that respecting locking order is important.
Maybe we should use the facility where zk can add the seqid to the name? So
maybe locks are named:
<zookeeper.znode.parent>/locks/<table_name>/r-seqid
or
<zookeeper.znode.parent>/locks/<table_name>/w-seqid
where the data then is details on who took the lock?
And you can't take a write lock if any instances of read lock outstanding?
I was thinking that maybe clients would be prepared to wait some time obtaining
a read lock but that they might fail fast if they could not get a read lock?
> Introduce a zk hosted table-wide read/write lock so only one table operation
> at a time
> --------------------------------------------------------------------------------------
>
> Key: HBASE-5494
> URL: https://issues.apache.org/jira/browse/HBASE-5494
> Project: HBase
> Issue Type: Improvement
> Reporter: stack
>
> I saw this facility over in the accumulo code base.
> Currently we just try to sort out the mess when splits come in during an
> online schema edit; somehow we figure we can figure all possible region
> transition combinations and make the right call.
> We could try and narrow the number of combinations by taking out a zk table
> lock when doing table operations.
> For example, on split or merge, we could take a read-only lock meaning the
> table can't be disabled while these are running.
> We could then take a write only lock if we want to ensure the table doesn't
> change while disabling or enabling process is happening.
> Shouldn't be too hard to add.
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